# Aeschylus

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## Posts posted by Aeschylus

1. ### cause of gravity

For example, the surface of a cylinder is bent but not curved. Also, the definitions of curvature does , eh?

We say a cylinder has extrinsic curvature, but no intrinsic curvature.

2. ### cause of gravity

The 2-D surfaces are just visual aids they do no represnt spacetime which is four dimensional (infact due to the signature of it's metric even two dimensional spacetime can never be proeperly represented in 3 dimensional approximately Euclidean space). The curvature of spacetime is something hat is very difficult to grasp, but people are already famir with the idea of two dimensional curved spaces, so it makes a good starting place.

3. ### Measure this!!!

lenght contarction refers to solid objects, so no we wouldn't call this lenght contraction. Of course the distance between the two points does vary from frame to frame like the length of a rod.

4. ### Measure this!!!

lenght contarction refers to solid objects, so no we wouldn't call this lenght contraction. Of course the distance between the two points does vary from frame to frame like the length of a rod.

5. ### help with a group question please

It's when they make you draw the multplictaion table for the trivial group that you should rise up and overthrow your maths teachers.

6. ### Aging in the Twin Paradox

What do you mean by a "mean zero difference"? if your talking in terms of total time expreinced then your dead wrong.

The noninertial twin always exprinces less time this is as in Minkowski spacetime the worldline of inertial observers are geodesics and therefore (because of the signtaure ofw the Minkowski metric) an observer whose worldine is a geodesic between two events will experince the maximal amount of time between those two events.

7. ### The Fouth Dimension

Not necessarily. GR has 6. Most people are taught classical relativity in high school and college unless one is perusing a degree in physics. The ideas of the standard model of relativity is largely because of the work done by Friedman. Einstein didnt like the idea until 2 years after the publication, then decided it served as a better mathematical model because it incorporate the electroweak forces. Later attempts at adding more dimension to the theory (to incorporate the strong force) have ben unsuccessful, though there are some models that may get some attention if a 5th force is discovered (hense the God Particle that will be looked for in Switzerland).

No offence, but did you just make all of that up!

1) spacetime in both the special and general theory of relativty has four dimensions

2) Friedmann's main contribution was his equations, howvere he died when relativty was still very young consquently he did not have a major influence on how relativty is viewed today.

3)The theory of the electroweak force orginated in the 1970's, Einstein died in 1955.

I think you may be slightly confused with Kaluza-Klein theory which was an early failed attempt at uniting general relativty and electromagnetism by introducing a fifth spatial dimensions, later some of the ideas from this theory were used in braneworld and stringy theories.

8. ### The Fouth Dimension

Well I found this website that explains the fourth dimension or also known as "tetrapace". [url']http://tetraspace.alkaline.org/[/url]

That site's a load of crap.

Spacetime has four dimensions (as Sverian indicated these days the convention is take time as the 'zeroth dimension', but it is only just a convetion and it doesn't really matter, infact rather than assigning numbers we could assign the names 'John', 'Paul', 'George' and 'Ringo' if we wanted), for any given obsrever 3 of them will be the three dimenisions of spaceas experinced by him (i.e. 'space' for some observer is a hypersurface of spacetime) and one will be his time dimensions.

I personally like to think of thing in terms of vector spaces, so a dimension to me is just the cardinality of the largest set of linearly indpendent vectors.

9. ### Undefined Time

In the current thread "Dark Energy" I presented a possible model of a non-isometric universe where the relative speed of the 'visible' universe might be determinable.

You must make this clear: relative to what (you cannot talk about the relative speed of an object without syaing what the speed is relative to otherwise it tells us nothing).

Although I would value any constructive criticism of the model, for the purpose's of this thread I would like to restate the idea I presented in my original post concerning the possible cosmological equivance of time-space. If it reasonably possible that I can with a degree of validity say such things as, "the sum of matter and energy is a constant", might it be possible that the pattern displayed by matter-energy be extended to the other major constituent of reality, time-space? In other words can I say such things as "at the point of the Big Bang event, the amount of space available to the universe was at its minimum and the amount of time available to the universe was at its maximum?"

aguy2

The problem is that enrgy really isn't conserved in spacetime that is not asymptotically flat. Knowldge of Newtonian physics and the basic principles of general relativty is enoguh to see thta this must be the case as enrgy is not conserevd in non-inertial refernce frames in Newtonian physics, yet in general relativty inertial and non-inertial refrence frames are given an equality of sorts.

ou msut also be clear what you mean by maximum aviadable space and maximum avidable time as thta to me has no obvious meaning.

10. ### Undefined Time

What would be the universe's relative speed? I think our problem is that we are looking at different scales. On the atomic scale you are of course right about 'rest mass' and 'relative speeds'' date=' but on a cosmological scale I can still say such things as, "the sum of matter and energy is a constant", can't I?

aguy2[/quote']

Well what dioyou mean by the universe's relative speed? For any relative speed you need to define what the speed is relative to! However there is a sort of 'refernce frame of the universe' (though don't read too much into that as it is merely the refernce frame where the universe is isotropic). But we still have a problem that energy can only truly be defined globally in flat spacetime, though if it is asymptotically flat we can have a good go at defining it, but there is no guarentee that the universe is asymptotically flat (though data from the CMBR certainly suggests the unievsre ay globally flat, but the problem is to prove the unievsre is flat you essientially need to measure a param,eter to 1000% accuracy).

11. ### A new idea for gravity??

the gravitaional field of a spherically symmetric object is spherically itself, the reasn for the phenumna you describe is not grvaity itslef, but the fact that the objects in question possess angular momentum.

12. ### How fast is gravity?

thankyou Aeschylus for your first paragraph reply."why didnt someone just say that in the first place".

your not here to discuss breakthroughs or new conceptions in science just to accept the orthadox opinion at the time.from now on i will just ask questions for information' date='however i dont sit comfortably with presumptions,probability,virtual as solid science it seems to be "our best guess is its this"and everyone just goes along with it kind of like sheep.Well thank goodness for scientists who question and say this is silly theirs got to be a better explanation,otherwise you lot would indeed believe the earth was flat." blackholes"...[/quote']

NO I did not say that, science is certainly open to new ideas, however it is firmly shut to metaphysical crackpottery.

13. ### Undefined Time

so' date=' if i were to travel at a certain velocity, to someone else, i would be a black hole, but to me i wouldn't?

does that mean that if someone survived the trip to the center of a black hole(ha), they may not know that they are in said black hole?[/quote']

No it means the opposite i.e. an object doesn't become a black hole because it is whizzing past you at x miles per hour.

14. ### Undefined Time

It's interesting, but you did mess up as graviational collapse is not dependet on relative velocity (also you shouldn't really talk about mas schanging with relative velcotiy as in all but the most out-dated or most basic text mass is defined as rest mass which is a Lorentz scalar, infact generally we don't even talk about 'relativstic mass even as it merely represents the energy of the object).

Consider this: in relativty there invaraibly exists a frame of refrence where you are travelling at such a speed that according to your reasoning you would collapse into a black hole. However you are not a black hole so clearly any line of reasoning that says you are must be incorrect.

15. ### How fast is gravity?

how can you debate when you tie your own hands.Im wrong' date='your right.We dont know something exists but this answer is yes this is no because at this moment in time physics says so.you are imoveable until the flavour of the month suits you."black holes....oh no nothing can escape a black hole..we ran the calculations using our formula and no impossible...."well what is the stance now in physics regarding blackholes??

Times change clever people devise formula and we learn more,whilst potential,relativistic,virtual,have there place its a thin line to be challenged tommorrow.

one more statement energy they say is equivalent to mass E=mc2,you can interpret it to mean were there is energy there is mass,were there is mass there is energy.also momentum is related to mass,however a photon has energy and momentum yet no mass.i agree but you could say it has relativistic mass because if we trap it in a container with perfect mirrors so the photons continuelly bounce back and forth.then in the boxes frame of reference the momentum is zero but the energy is not.so light would add to the mass of the box.You could measure this in principle by an increase in inertia when the box is accelerated or by gravitational pull.But we define mass today as invarient mass,so in this case mass wouldnt be conserved so all we can now say is the mass of a box of light is more than the mass of the box and the sum of the masses of the photons (the latter being zero).we now see energy doesnt have to have mass.mass is not equivalent to energy.So does light have mass,we say no but its open to how you interpret it.

The main problem you wont accept is i believe and i hope its soon,someone will provide the formula and do the math showing gravity does travel FTL.Physics cannot measure accurately wether it does or doesnt,you can only calculate its effects which isnt the same thing.Can you not agree to disagree like gentelmen and not lead to my posts being removed.

I just hope when im proved right your all still here, you will all jump on the bandwagon "i didnt say it couldnt travel FTL"[/quote']

The p[roblem is philbo this board is about science, peopel here want to know what science says, not uninformed opinion. Science ius sunject to change but don't expect people to give the time of day to random unsupported hypothesises.

Most of your post is irrelvenat to the subjecct at hand, but I'lll answer the relevenat point. There is no reason whatsovere to believe that some future theory willl produce FTL gravity; our best theory of gravity (genetal relativity currently says gravity acts at c and it would gnereally be expected that any new htoery presevres Lorrentz invaraince which would limit the speed of gravity to c or less.

16. ### Undefined Time

American Heritage Dictionary

mass-energy equivalence: noun' date=' the physical principle that a measured quantity of energy is equivalent to a measured quantity of mass. The equivalence is expressed by Einsteins equation E=MC2.[/quote']

My advise to you is to look in a modern physics book not a dictionary, mass and energy are not equiavelnt as the enrgy of the object is depedent on that object's relative speed whereas the mass is not (and don't let anyone tell you otherwise as mass is defined to be the rest mass).

17. ### How fast is gravity?

no it breaks the law of conservation of energy.It has no source.if you need me to give more read both Newton & Einstein they are just as flumexed.

Do you understand the concept of gravaitainal potential energy? Certianly gravity does not break the law of conservation of energy. In general relativty the conservation of enrgy isn't paraticularly important anyway.

18. ### A quick answer to philbo

Yes it can be shown that say for examaple a planet orbiting a star it is the instaneous psotion of the star that is important to how a star will affect that planet grvaitionally, BUT this not what we talk about when we talk about 'the speed of gravity'.

Light is an electromagnetic wave and it is produced by a 'changing' electrogmanetic field. Electromagnetism and gravity are simalir in sevral ways (the most obvious being the inverse square law), in general relativty 'changing' gravitatioanl fields produce gravitational waves which is analgous to light, it is the speed of these wave sthat we call the speed of gravity; stars generally do not produce gravtitional waves (they do not occur in spherically symmetric spacetime).

The fact that it is the instaneous postion of a body thta is important in your example is not important as this does not necessarily imply instaneous transfer of information as it is grvaitybwaves thta represent the transfer of information in gravitational fields (or to look at it another way the gravtional field itself is not 'changing').

19. ### co2 help

I rember when I was in school someone swallowed a piece of chalk during chemistry - never do this ever!

20. ### Undefined Time

If it wa sonly the factor of c^2 we had to worry about then we would say thta mass and enrgy were equivalent, but it's the fact that the total energy of an object in some frame is not depedent only on it's mass.

21. ### Finite Sets of Infinite Things

had an idea in class the the other day...feel free to add on or modify for whatever' date=' just a rabbit trail of thought....

Let A = { pi , 2^(1/2) }

A only contains 2 items and so Card(A) = 2 => there exists a bijective function from A to the natural numbers of order 2 => A is finite...probably didnt need to prove it but there it is.

Write the items in A as sets themselfs as such

pi = {3, 1, 4, 1, 5, 9, ... }

2^(1/2) = { 1, 4, 1, 4, 2, 1, ... }

So can A be rewritten as A = { {3 1 4 1 5 9...} , {1 4 1 4 2 1...} } ?

Would this imply that A has an infinite number of things dispite that it is a finite set? Or is it just my notation and how i'm defining things?

Any interesting ideas on where i could go from here?[/quote']

Well no, becasue it's the numbers themselves not the digits in their decimal representation (and it must be added thta choosing them to be represnted as decimals is completely arbitay) that are elements of the set.

Of course you could have a set A = {R ,R^2} this set has two elements yet it's elements are infinite sets. Of course there's nothing particualry remarkable about that as it is not the elements of the sets R and R^2 that belong to A, but the sets themselves.

22. ### Undefined Time

It means you don't travel at c. There are no frames that travel at c or greater relative to any other inertial frame.

23. ### Equations

ok' date=' it is possible i am wrong, but from sites such as:

http://www.vttoth.com/emc2.htm

&

i thought that einstein had played a major role but was not the one to create the whole e=mc^2 formula.

[i']i could be wrong, but those sites claim it is a common and justified thing to think it is einstiens, so i dont know...[/i]

The first site is rather whiney, but all it says is that E = mc^2 should not be called Einstein's equation (instead it prefers to give the title to what I suppose would more commnly be called Einstein's fgield equation), it certainly does not say that E = mc^2 was not EInstein's.

The second site is rather conmtetious is trie sto completly obscur ethe fact that Einstein was the first to derive the genral case.

24. ### Time travelling

The one about all motion/speed being relative?

I can understand that but why couldn't something leave a galaxy and stop moving completely??

Granted it would still be relative to all the other galaxies in the universe but it wouldn't be travelling through space' date=' would it??

Which would mean the time dilation effect of travelling closer to the speed of light to slow time would be affecting this object in the least possible way.[/quote']

Time dialtion is dependent on relative speed only, not on spatial sepration (though spatial sepreation certianly is important to simulataneity), so if I was travelling at 0.99c relative to a very far awya galaxy then from my point of view 'clocks on that galaxy would appear to me slower and from their point of view my clocks would be running slower. Of course in there own refrence frame evryone considers themself to be at rest.

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